Selection of Seeds of Common Native and Non-Native Plants by Granivorous Rodents in the Northeastern United States

Post-dispersal seed predation by rodents represents a potentially important element of biotic resistance to plant invasion. Selection for five different types of seeds by granivorous rodents was studied in maple-beech forests, old fields and conifer plantations in Madison County, New York. Rodents visited dishes containing equal masses of seeds of the native Cornus amomum and Rubus idaeus, and the non-native Lonicera morrowii, Rhamnus cathartica and Rosa multiflora. Greater masses of C. amomum and R. idaeus seeds were consumed during a night of mammal visitation than of the three non-native species, and pattern of selection did not differ among habitats. Rodents encountered seed dishes sooner in forested habitats than old fields. The primary seed predators in our region, Peromyscus spp., were more common at forests and plantations than old fields. Patterns of habitat use by Peromyscus spp. may aid in resisting invasion of intact forests by invasive plants; however, selection of native over non-native seeds may facilitate differential establishment of non-native invaders.

INTRODUCTION

Many of the persistent non-native invaders of old fields and other early successional habitats in the northeastern United States are woody plants, including Lonicera (bush honeysuckles), Rhamnus (buckthorns) and Rosa multiflora (multiflora rose; Luken and Thieret, 1996; Hunter and Mattice, 2002; Knight et al, 2007). These and other woody invaders have become established in forest interiors, particularly following disturbance (Hunter and Mattice, 2002; Huebner, 2003; Huebner and Tobin, 2006; Mascara and Schnitzer, 2007), raising concerns about the management of natural areas that have a history of agricultural or silvicultural land use.

Post-dispersal seed predation can affect the abundance and spatial distribution of plants during succession (De Steven, 1991; Gill and Marks, 1991; Davidson, 1993; Hulme, 1997). If non-native plants encounter lower rates of seed prédation relative to natives, they might have an advantage over potential competitors (Elton, 1958). Mammal seed predators have exhibited preferences among available seed types in forested (Myster and Pickett, 1993; Meiners and Stiles, 1997) and desert (Murray and Dickman, 1997) ecosystems. The invasive Norway maple (Acer platanoides) experiences less post-dispersal seed predation dian its native congener, sugar maple (A. saccharum), in forests of northeastern North America (Meiners, 2005). In a study of 22 native and 21 non-native forbs and graminoids in Ontario, however, Blaney and Kotanen (2001) found no evidence that seed predators selected non-natives differently than natives. Seed predation rates can vary across micro- and macro-habitats (Webb and Willson, 1985; Gill and Marks, 1991; Myster and Pickett, 1993), which might alter successional trajectories and the outcome of plant invasions.

We conducted an experiment to determine the potential role of seed predators in regulating success of several common non-native invaders relative to native species. Cafeteria-style dietary trials were conducted in late successional maple-beech forests and in two common early-successional habitats, abandoned agricultural fields and abandoned conifer plantations.

STUDY AREA

Nine study plots were established on properties owned by Colgate University in Madison County, New York (47°38-40'N, 75°32-38'W). One plot was established in each of maple-beech forest, old field and conifer plantation at each of the following study sites: lands adjacent to the Colgate University campus (Campus), the southern portion of the Bewkes Nature Preserve (Bewkes South), and the northern portion of the Bewkes Nature Preserve (Bewkes North) . Plots in maple-beech forests and old fields were 30 X 50 m; plots in plantations were 30 × 30 m to maintain consistency with other research at these study sites (McCay and McCay, in press).

Maple-beech stands were aged 60-1 20 y based on increment cores of the largest individuals within the plots. …

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